libtool: compile: x86_64-pc-linux-gnu-gcc -DHAVE_CONFIG_H -I. -I. -I./include -Iinclude -I./src -Wall -g -fexceptions -march=native -O2 -g0 -c src/closures.c -fPIC -DPIC -o src/.libs/closures.o amd64box ~ # emerge --info | grep CFLAGS CFLAGS="-march=native -O2 -g0"
your -g0 overrode the -g. ignoring that, see bug 378663.